Role of adrenal medulla in morphine-induced hyperthermia through central action

The role of the adrenal glands, in morphine-induced hyperthermia was studied in normal, chemically-sympathectomized, adrenalectomized, adrenal-demedullated or splanchnicotomized rats. 2. In restrained female rats, 5 mg/kg morphine produced hyperthermia whereas 20 mg/kg and 40 mg/kg produced hyperthermia. 3. After adrenalectomy, 5 mg/kg morphine did not produce hyperthermia. 4. After adrenal-demedullation or adrenal-denervation (splanchnicotomy), 5 mg/kg morphine did not produce hyperthermia. 5. The results suggest that, in the rat, the adrenal medulla plays an important role in morphine-induced hyperthermia, and that morphine acts centrally to stimulate the medulla.